The three-volume proceedings LNCS 12491, 12492, and 12493 constitutes the proceedings of the 26^th International Conference on the Theory and Application of Cryptology and Information Security, ASIACRYPT 2020, which was held during December 7-11, 2020. The conference was planned to take place in Daejeon, South Korea, but changed to an online format due to the COVID-19 pandemic.

The total of 85 full papers presented in these proceedings was carefully reviewed and selected from 316 submissions. The papers were organized in topical sections as follows:

Part I: Best paper awards; encryption schemes.- post-quantum cryptography; cryptanalysis; symmetric key cryptography; message authentication codes; side-channel analysis.

Part II: public key cryptography; lattice-based cryptography; isogeny-based cryptography; quantum algorithms; authenticated key exchange.

Part III: multi-party computation; secret sharing; attribute-based encryption; updatable encryption; zero knowledge; blockchains and contact tracing.